public class Role
{
    [Key]
    public string Role { get; set; }
    public virtual ICollection<Template> Templates { get; set; }
}
public class Template
{
    [Key][Required]
    public string TemplateID { get; set; }
    [Required]
    public string Header { get; set; }
    [Required][DataType(DataType.MultilineText)]
    public string Description { get; set; }
    public virtual ICollection<CorrespondenceRole> Roles { get; set; }
}

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Template>()
        .HasMany(c => c.Roles)
        .WithMany(c => c.Templates)
        .Map(m => m.ToTable("Template_Roles")
            .MapLeftKey("TemplateID")
            .MapRightKey("Role"));
}

public ActionResult Edit(Template ctemplate)
{
    db.Entry(ctemplate).State = EntityState.Modified;
    db.SaveChanges();
}

public ActionResult Edit(Template ctemplate)
{
    Template ct = db.Templates.Find(ctemplate.TemplateID);
    ct.Roles.Add(db.Roles.Find("Other Party"));
    db.Entry(ct).State = EntityState.Modified;
    db.SaveChanges();
}

db.Entry(ct).State = EntityState.Modified;

foreach (var entity in db.Roles.Where(cr => cr.TemplateID == ct.ID))
    db.Roles.Remove(entity);

foreach (Role cr in ct.Roles)
    db.Roles.Add(cr);

db.SaveChanges();

public ActionResult Edit(Template ctemplate)
{
    db.Entry(ctemplate).State = EntityState.Modified;
    foreach (CorrespondenceRole role in ctemplate.Roles)
    {
        //Change role State -> EntityState.Modified
    }
    db.SaveChanges();
}